Bezier editing produces very odd results in EPSG 7856 CRS

[jaysenmarais]

When I try to use the QGIS Bezier Editing plugin v1.3.8 in QGIS 3.38 (or 3.32) with a document whose CRS is EPSG 7856 (Eastern Australia) the bezier handles and curves are offset from each other. This makes beziers very difficult to create or edit. Additionally the bezier handles are not co-linear when dragging a point (even though I have no modifier keys pressed on the keyboard). Please see the view below.

https://github.com/user-attachments/assets/6fdbfc07-fc7f-42d0-8d74-ed12179105d5

Reproduction steps

1. Create a new document in QGIS 3.38
2. Set the document CRS to EPSG 7856
3. Create a new temporary scratch layer with geometry type of polygon and CRS of EPSG 7856
4. Pan to a location on the east coast of Australia (such as 516348, 7129949)
5. Zoom into a high magnification level (such as 1:100)
6. Select the Bezier Edit tool
7. Attempt to draw a bezier curve

Note that the bezier handles are offset from the curve. In some cases (I think it is related to the easting/northing) the curve will fail to draw completely and the logs will be full of warnings along the lines of the following

[tmizu23]

Thank you for the report. I tried with the conditions you showed, but I couldn't reproduce the issue in my environment. Can you think of any other conditions that might cause the issue?

Windows 11 QGIS 3.38.2 Bezier Editing v1.3.8